The proposed research is aimed at studying aspects of the assembly and function of the outer membrane in gram negative bacteria. Its specific objectives are: 1) To carry out a genetic analysis of the rfa region in E. coli K12 and to determine the effect of rfa mutations on the protein composition of the outer membrane. 2) To study the mechanism of protein secretion using fusions of secreted proteins to alkaline phosphatase. 3) To study the mechanism by which bacteriophage epsilon 15 alters the cell surface O-antigen of its Salmonella host. This work is possible because of the recent advances in cloning technology and the technique of gene and operon fusion.